This invention pertains to methods for making data storage cards. This invention also pertains to non-rotating magnetic recording media.
Credit cards and automatic teller cards typically contain strips of magnetic recording media for storing about 250 bytes of data. Such cards typically comprise a plastic such as PVC with particulate media applied thereto in the form of a strip. The particulate media comprise magnetic particles suspended in a binder, applied to the card by a process such as silk screen printing. The magnetic particles are typically an iron oxide particle such as xcex3 Fe2O3.
Particulate media in a binder are used in other types of memory applications, e.g. magnetic tape. While particulate media are adequate for certain applications, there is a limit to the data recording density that can be achieved using such media. Since magnetic tape can be made very thin, and a large amount of tape can be stored on a reel, particulate media type magnetic tape remains practical, despite the data storage density limitations of particulate media.
One can achieve much greater recording density using thin film recording media. As its name implies, thin film media comprise a thin, continuous magnetic film such as a cobalt alloy film. Such films are typically formed by sputtering onto a substrate. The major application for thin film magnetic recording media is hard magnetic disks.
While it might be tempting to try to sputter a magnetic film directly onto a plastic card, there are a number of problems that one would have to solve first.
1. Sputtering is typically done in a high vacuum environment. Accordingly, if one wanted to sputter onto a credit card, one would have to find a credit card material that would not out-gas contaminants that would poison the sputtering process.
2. Many sputtering processes are performed at high temperatures. Accordingly, one would have to either use a low temperature sputtering process, or find a plastic material that could survive high temperatures. Since one can generally achieve greater recording density using high temperature sputtering processes, it would be desirable to find a way to use high temperature sputtering processes when making credit cards.
Current specifications for credit cards require that they be flexible. Accordingly, magnetic recording structures within such a card should preferably be bendable. The credit card should also be inexpensive to manufacture, and should also be reliable.
It is an object of some embodiments of the present invention to provide a new method for manufacturing a credit card type data storage device using thin film technology.
It is also an object of some embodiments of the present invention to provide a credit card data storage device using thin film recording media.
A method in accordance with the invention comprises the step of sputtering a thin magnetic film on a thin substrate, and then affixing the substrate to a credit card. The thin substrate is sufficiently flexible such that it can be mounted on the credit card. In one embodiment, the substrate is a silica-containing material such as glass or glass ceramic. Alternatively, the substrate can be a metal foil. Of importance, in some embodiments the substrate is capable of withstanding the temperature used in a high temperature sputtering apparatus.
The card need not be a credit card. In other embodiments, it is an identification card, or other form of data storage card.